Disposable absorbent products have met with widespread acceptance in the marketplace for a variety of applications, including infant and adult incontinence care, in view of the manner in which such products can provide effective and convenient liquid absorption and retention while maintaining the comfort of the wearer. However, experience has shown that a need exists for thinner, more discreet, garment-like products that can exhibit a dry surface to the skin during use. Small quantities of liquid trapped in nonwoven fabric layers on the surface of an absorbent product can undesirably hydrate the stratum corneum, the barrier layer of the skin, and increase the rate of diffusion of skin irritants into the skin. Potential skin irritants are present in urine and feces, as well as in skin cleaning products.
In the design of conventional wood pulp fluff/superabsorbent polymer (SAP) absorbent cores, it is widely recognized that cores with higher concentrations of superabsorbent polymer exhibit longer (i.e. poorer) acquisition times and lower (i.e. better) liquid rewet. Furthermore, it follows that a z-direction gradient of superabsorbent polymer, with a SAP-rich surface concentration, will also exhibit longer (i.e. poorer) acquisition times and lower (i.e. better) rewet relative to a core with a homogeneous distribution of SAP. It has been difficult, however, to find ways to boost the dryness of an absorbent core without generating unacceptably long acquisition times. Long acquisition times are unwanted because they promote leakage from an absorbent product.
Conventional technology to improve the acquisition time of cores with increasingly high concentrations of SAP has involved the use of nonwoven surface layers that promote liquid spreading over the surface of a slowly absorbing core in order to allow absorption to occur over a greater surface area. This surface spreading of free liquid often leads to leakage from the side of the core, and/or leakage at the front of the core.